I’ve been pretty happy with KMail from KDE in the past few years (and it’s running almost 24/7). You might also want to look into web-based solutions such as RoundCube webmail (http://roundcube.net/), which, depending on your connection speed, may be quick enough.
A friend of mine goes a different route, setting up an email server locally (I believe he uses the Kerio Mailserver), using his ISP as the smarthost, and accessing the mail using TheBat, Thunderbird, and other mail clients locally; This has the advantage of fast access combined with multi-client accessibility (which is rather nice to have if you have more than just one computer and/or client